NAME

pthread_getattr_default_np, pthread_setattr_default_np, - get or set default thread-creation attributes

LIBRARY

POSIX threads library (libpthread, -lpthread)

SYNOPSIS

#define _GNU_SOURCE             /* See feature_test_macros(7) */#include <pthread.h>

int pthread_getattr_default_np(pthread_attr_t *attr);int pthread_setattr_default_np(const pthread_attr_t *attr);

DESCRIPTION

The pthread_setattr_default_np() function sets the default attributes used for creation of a new thread—that is, the attributes that are used when pthread_create(3) is called with a second argument that is NULL. The default attributes are set using the attributes supplied in *attr, a previously initialized thread attributes object. Note the following details about the supplied attributes object:

•: The attribute settings in the object must be valid.
•: The stack address attribute must not be set in the object.
•: Setting the stack size attribute to zero means leave the default stack size unchanged.

The pthread_getattr_default_np() function initializes the thread attributes object referred to by attr so that it contains the default attributes used for thread creation.

ERRORS

EINVAL: (pthread_setattr_default_np()) One of the attribute settings in attr is invalid, or the stack address attribute is set in attr.
ENOMEM: (pthread_setattr_default_np()) Insufficient memory.

VERSIONS

These functions are available since glibc 2.18.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
pthread_getattr_default_np (), pthread_setattr_default_np ()	Thread safety	MT-Safe

STANDARDS

These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in their names.

EXAMPLES

The program below uses pthread_getattr_default_np() to fetch the default thread-creation attributes and then displays various settings from the returned thread attributes object. When running the program, we see the following output:

$ ./a.outStack size:          8388608Guard size:          4096Scheduling policy:   SCHED_OTHERScheduling priority: 0Detach state:        JOINABLEInherit scheduler:   INHERIT

Program source

#define _GNU_SOURCE#include <err.h>#include <errno.h>#include <pthread.h>#include <stdio.h>#include <stdlib.h>static voiddisplay_pthread_attr(pthread_attr_t *attr){
    int s;
    size_t stacksize;
    size_t guardsize;
    int policy;
    struct sched_param schedparam;
    int detachstate;
    int inheritsched;
    s = pthread_attr_getstacksize(attr, &stacksize);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getstacksize");
    printf("Stack size:          %zd\n", stacksize);
    s = pthread_attr_getguardsize(attr, &guardsize);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getguardsize");
    printf("Guard size:          %zd\n", guardsize);
    s = pthread_attr_getschedpolicy(attr, &policy);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy");
    printf("Scheduling policy:   %s\n",
           (policy == SCHED_FIFO) ? "SCHED_FIFO" :
           (policy == SCHED_RR) ? "SCHED_RR" :
           (policy == SCHED_OTHER) ? "SCHED_OTHER" : "[unknown]");
    s = pthread_attr_getschedparam(attr, &schedparam);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getschedparam");
    printf("Scheduling priority: %d\n", schedparam.sched_priority);
    s = pthread_attr_getdetachstate(attr, &detachstate);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate");
    printf("Detach state:        %s\n",
           (detachstate == PTHREAD_CREATE_DETACHED) ? "DETACHED" :
           (detachstate == PTHREAD_CREATE_JOINABLE) ? "JOINABLE" :
           "???");
    s = pthread_attr_getinheritsched(attr, &inheritsched);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched");
    printf("Inherit scheduler:   %s\n",
           (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
           (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
           "???");}intmain(void){
    int s;
    pthread_attr_t attr;
    s = pthread_getattr_default_np(&attr);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_getattr_default_np");
    display_pthread_attr(&attr);
    exit(EXIT_SUCCESS);}